Significant degrees of biotransformation of volatile anesthetics have been well demonstrated, and divergent sources suggest Michaelis -Menton kinetics are obeyed. However, previous studies (including my own work) have failed to measure the rate at which the anesthetics are metabolized. No in vivo work in man has assessed the concentration dependence of anesthetic metabolism by documenting the Vmax and Km. Without this knowledge it is impossible to accurately predict the impact of biotransformation on the maintenance of an anesthetizing concentration of a volatile agent. Furthermore, numerous studies have linked anesthetic metabolism with organ toxicites, and therefore a method of measurement of the kinetic parameters of anesthetic metabolism may allow assessment of interventions likely to increase anesthetic toxicities by their influence on biotransformation such as premedications or other drugs. We propose to determine the kinetic parameters Vmax and Km in man for halothane enflurane, isoflurane and methoxyflurane by measuring the uptake per minute of anesthetic under conditions where uptake by inactive tissue depots can be eliminated or estimated. The residual uptake would be that due to metabolism. The implications to anesthetic induction will be quantified by measuring the relationship between the inspired and alveolar anesthetic concentrations during the anesthetic administration. Liver and renal functions will be measured before and after the exposure to ascertain whether subtle differences occur and can be correlated with the rate of anesthetic metabolism. The significance of this work lies both in the immediate information likely to result, and the development of a unique and non-invasive method for the measurement of the kinetic parameters of volatile anesthetic biotransformation in man.